1. Field of the Invention
The present invention relates to a laser light quantity control device for controlling a multi-beam semiconductor laser having a plurality of light emitting portions for emitting laser beams, and an image forming apparatus for performing image formation using the light quantity control device.
2. Related Background Art
Conventionally, a laser element is controlled by a light quantity control device. In light quantity adjustments using a multi-beam semiconductor laser (laser element) having a plurality of light emitting portions for producing a plurality of laser beams in an image forming apparatus such as a laser beam printer, after light quantity adjustments for one light emitting portion are complete, adjustments for the next light emitting portion are performed.
That is, after the light quantity of one light emitting portion has reached a target light quantity and adjustments are complete, the adjustments for the next light emitting portion are started.
However, in such conventional method, light emitting portions which are subjected to adjustments later have larger influences of heat produced by light emitting portions that have been already adjusted. In general, the output light quantity of a semiconductor laser element decreases as its temperature rises even when the laser current remains the same. For this reason, the laser current of a light emitting portion which has undergone light quantity adjustments in a high-temperature state consequently becomes large. In particular, in a laser element of a multi-beam semiconductor laser, the output light quantity of a light emitting portion which has undergone light quantity adjustments last in a high-temperature state under the influence of heat from other light emitting portions is different from that of a light emitting portion which has undergone light quantity adjustments first in a low-temperature state without having any influence of heat from other light emitting portions, when they are made to emit laser beams simultaneously.